What tattooist includes excessively (3)
I believe the answer is:
too
'excessively' is the definition.
('too' can be a synonym of 'excessively')
'what tattooist includes' is the wordplay.
'includes' indicates the answer is hidden within the clue.
'TOO' can be found hidden inside 'what tattooist'.
(Other definitions for too that I've seen before include "On top - also" , "As well; in addition" , "Furthermore" , "Moreover, in addition" , "As well, also" .)